Shoddy recordkeeping led to significant overstating of terrorism convictions and other inaccuracies by a Justice Department branch that coordinates U.S. attorneys’ offices across the country, according to a federal audit.

The audit by the department’s inspector general, Michael E. Horowitz, found that the Executive Office for U.S. Attorneys (EOUSA) overstated the number of terrorism-related defendants who had been found guilty in fiscal 2009 by 13 percent and then overstated the same statistic in fiscal 2010 by 26 percent.

The executive office, which oversees 93 U.S. attorneys’ offices, also overstated by 19 percent the number of defendants sentenced to prison in 2010, the audit found.

In sum, Horowitz said, his office found that EOUSA inaccurately reported eight categories of statistics by significant margins.

The numbers reported by the branch generally reflect the majority of terrorism cases brought by the Justice Department, officials said. EOUSA reported 193 in 2009 and 236 in 2010, officials said.

The report follows up on a 2007 audit that found that the department as a whole — including the FBI and the criminal division — did not accurately report terrorism-related statistics.

“These inaccuracies are important in part because DOJ management and Congress need accurate terrorism-related statistics to make informed operational and budgetary decisions,” Horowitz said in a statement accompanying the audit’s release.

In a 2009 sample of 103 defendants, auditors found that 11 were reported as guilty on terrorism charges and should not have been; nine of them were found guilty in 2008. One of the nine was convicted in a narcotics and money-laundering case. The other two had their charges dismissed.

“We consider this amount of deviation . . . to be significant,” Horowitz said.

In a 2010 sample of 292 defendants who were reported to have been convicted, auditors found that 17 of the verdicts occurred in 2009. Three of them had already been recorded in 2009 and so were counted twice.

The auditors also found a number of misreported cases.

In 2010, one conviction appeal was coded as a domestic terrorism case when it involved animal fighting.

In a second case, a bank robbery conviction was reported as a terrorism-related hoax.

Also that year, two cases classified as terrorism-related dealt with organized-crime drug-dealing.

Some errors resulted from EOUSA reporting the date prosecutors logged the case into the Legal Information Office Network Systems database, not the date of the conviction or other outcome.

EOUSA Deputy Director Norman Wong said the agency concurred with suggestions for improvement and will work to make them.